Novel dyes and use thereof in imaging members and methods

ABSTRACT

There are described novel rhodamine dye compounds and imaging members and imaging methods, including thermal imaging members and imaging methods, utilizing the compounds. The dye compounds exhibit a first color when in the crystalline form and a second color, different from the first color, when in the liquid, amorphous form.

REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of provisional applicationserial No. 60/451,208, filed Feb. 28, 2003.

[0002] This application is related to the following commonly assignedUnited States patent applications and patents, the disclosures of all ofwhich are hereby incorporated by reference herein in their entirety:

[0003] U.S. patent application Ser. No. (______; filed on even dateherewith (Attorney Docket No. C-8544AFP);

[0004] U.S. Pat. No. 6,537,410 B2;

[0005] U.S. patent application Ser. No. 10/151,432 filed May 20, 2002 ),(U.S. patent application No. US2003/0125206 A1); and

[0006] U.S. Pat. No. 6,054,246.

FIELD OF THE INVENTION

[0007] This invention relates to novel compounds and, more particularly,to compounds which exhibit one color in the crystalline form and asecond, different color in the liquid, or amorphous, form. Alsodescribed are imaging members and methods, including thermal imagingmembers and methods, utilizing the compounds.

BACKGROUND OF THE INVENTION

[0008] The development of thermal print heads (linear arrays ofindividually-addressable resistors) has led to the development of a widevariety of thermally-sensitive media. In some of these, known as“thermal transfer” systems, heat is used to move colored material from adonor sheet to a receiver sheet. Alternatively, heat may be used toconvert a colorless coating on a single sheet into a colored image, in aprocess known as “direct thermal” imaging. Direct thermal imaging hasthe advantage over thermal transfer of the simplicity of a single sheet.On the other hand, unless a fixing step is incorporated, direct thermalsystems are still sensitive to heat after thermal printing. If a stableimage is needed from an unfixed direct thermal system, the temperaturefor coloration must be higher than any temperature that the image islikely to encounter during normal use. A problem arises in that thehigher the temperature for coloration, the less sensitive the mediumwill be when printed with the thermal print head. High sensitivity isimportant for maximum speed of printing, for maximizing the longevity ofthe print head, and for energy conservation in mobile, battery-poweredprinters. As described in more detail below, maximizing sensitivitywhile maintaining stability is more easily achieved if the temperatureof coloration of a direct thermal medium is substantially independent ofthe heating time.

[0009] Thermal print heads address one line of the image at a time. Forreasonable printing times, each line of the image is heated for aboutten milliseconds or less. Storage of the medium (prior to printing or inthe form of the final image) may need to be for years, however. Thus,for high imaging sensitivity, a high degree of coloration is required ina short time of heating, while for good stability a low degree ofcoloration is required for a long time of heating.

[0010] Most chemical reactions speed up with increasing temperature.Therefore, the temperature required for coloration in the short heatingtime available from a thermal print head will normally be higher thanthe temperature needed to cause coloration during the long storage time.Actually reversing this order of temperatures would be a very difficulttask, but maintaining a substantially time-independent temperature ofcoloration, such that both long-time and short-time temperatures forcoloration are substantially the same, is a desirable goal that isachieved by the present invention.

[0011] There are other reasons why a time-independent colorationtemperature may be desirable. It may, for example, be required toperform a second thermal step, requiring a relatively long time ofheating, after printing. An example of such a step would be thermallamination of an image. The temperature of coloration of the mediumduring the time required for thermal lamination must be higher than thelamination temperature (otherwise the medium would become colorizedduring lamination). It would be preferred that the imaging temperaturebe higher than the lamination temperature by as small a margin aspossible, as would be the case for time-independent temperature ofcoloration.

[0012] Finally, the imaging system may comprise more than onecolor-forming layer and be designed to be printed with a single thermalprint-head, as described in the above-mentioned patent application Ser.No. 10/151,432. In one embodiment of the imaging system, the topmostcolor-forming layer forms color in a relatively short time at arelatively high temperature, while the lower layer or layers form colorin a relatively long time at a relatively low temperature. An idealtopmost layer for this type of direct thermal imaging system would havetime-independent temperature of coloration.

[0013] Prior art direct thermal imaging systems have used severaldifferent chemical mechanisms to produce a change in color. Some haveemployed compounds that are intrinsically unstable, and which decomposeto form a visible color when heated. Such color changes may involve aunimolecular chemical reaction. This reaction may cause color to beformed from a colorless precursor, the color of a colored material tochange, or a colored material to bleach. The rate of the reaction isaccelerated by heat. For example, U.S. Pat. No. 3,488,705 disclosesthermally unstable organic acid salts of triarylmethane dyes that aredecomposed and bleached upon heating. U.S. Pat. No. 3,745,009 reissuedas U.S. Reissue Pat. No. 29,168 and U.S. Pat. No. 3,832,212 discloseheat-sensitive compounds for thermography containing a heterocyclicnitrogen atom substituted with an —OR group, for example, a carbonategroup, that decolorize by undergoing homolytic or heterolytic cleavageof the nitrogen-oxygen bond upon heating to produce an RO+ ion or RO′radical and a dye base or dye radical which may in part fragmentfurther. U.S. Pat. No. 4,380,629 discloses styryl-like compounds thatundergo coloration or bleaching, reversibly or irreversibly, viaring-opening and ring-closing in response to activating energies. U.S.Pat. No. 4,720,449 describes an intramolecular acylation reaction thatconverts a colorless molecule to a colored form. U.S. Pat. No. 4,243,052describes pyrolysis of a mixed carbonate of a quinophthalone precursorthat may be used to form a dye. U.S. Pat. No. 4,602,263 describes athermally-removable protecting group that may be used to reveal a dye orto change the color of a dye. U.S. Pat. No. 5,350,870 describes anintramolecular acylation reaction that may be used to induce a colorchange. A further example of a unimolecular color-forming reaction isdescribed in “New Thermo-Response Dyes: Coloration by the ClaisenRearrangement and Intramolecular Acid-Base Reaction Masahiko Inouye,Kikuo Tsuchiya, and Teijiro Kitao, Angew. Chem. Int. Ed. Engl. 31, pp.204-5 (1992).

[0014] In all of the above-mentioned examples, control of the chemicalreaction is achieved through the change in rate that occurs withchanging temperature. Thermally-induced changes in rates of chemicalreactions in the absence of phase changes may often be approximated bythe Arrhenius equation, in which the rate constant increasesexponentially as the reciprocal of absolute temperature decreases (i.e.,as temperature increases). The slope of the straight line relating thelogarithm of the rate constant to the reciprocal of the absolutetemperature is proportional to the so-called “activation energy”. Theprior art compounds described above are coated in an amorphous stateprior to imaging, and thus no change in phase is expected or describedas occurring between room temperature and the imaging temperature. Thus,as employed in the prior art, these compounds exhibit stronglytime-dependent coloration temperatures. Some of these prior artcompounds are described as having been isolated in crystalline form.Nevertheless, in no case is there mentioned in this prior art any changein activation energy of the color-forming reaction that may occur whencrystals of the compounds are melted.

[0015] Other prior art thermal imaging media depend upon melting totrigger image formation. Typically, two or more chemical compounds thatreact together to produce a color change are coated onto a substrate insuch a way that they are segregated from one another, for example, asdispersions of small crystals. Melting, either of the compoundsthemselves or of an additional fusible vehicle, brings them into contactwith one another and causes a visible image to be formed. For example, acolorless dye precursor may form color upon heat-induced contact with areagent. This reagent may be a Bronsted acid, as described in “ImagingProcesses and Materials”, Neblette's Eighth Edition, J. Sturge, V.Walworth, A. Shepp, Eds., Van Nostrand Reinhold, 1989, pp. 274-275, or aLewis acid, as described for example in U.S. Pat. No. 4,636,819.Suitable dye precursors for use with acidic reagents are described, forexample, in U.S. Pat. No. 2,417,897, South African Patent 68-00170,South African Patent 68-00323 and Ger. Offenlegungschrift 2,259,409.Further examples of such dyes may be found in “Synthesis and Propertiesof Phthalide-type Color Formers”, by Ina Fletcher and Rudolf Zink, in“Chemistry and Applications of Leuco Dyes”, Muthyala Ed., Plenum Press,New York, 1997. The acidic material may for example be a phenolderivative or an aromatic carboxylic acid derivative. Such thermalimaging materials and various combinations thereof are now well known,and various methods of preparing heat-sensitive recording elementsemploying these materials also are well known and have been described,for example, in U.S. Pat. Nos. 3,539,375, 4,401,717 and 4,415,633. U.S.Pat. Nos. 4,390,616 and 4,436,920 describe image forming memberscomprising materials similar to those of the present invention. Thematerials described therein are fluoran dyes for use in conjunction witha developer, and there is not report of image formation upon melting inthe absence of a developer.

[0016] Prior art systems in which at least two separate components aremixed following a melting transition suffer from the drawback that thetemperature required to form an image in a very short time by a thermalprint-head may be substantially higher than the temperature required tocolorize the medium during longer periods of heating. This difference iscaused by the change in the rate of the diffusion needed to mix themolten components together, which may become limiting when heat isapplied for very short periods. The temperature may need to be raisedwell above the melting points of the individual components to overcomethis slow rate of diffusion. Diffusion rates may not be limiting duringlong periods of heating, however, and the temperature at whichcoloration takes place in these cases may actually be less than themelting point of either individual component, occurring at the eutecticmelting point of the mixture of crystalline materials.

[0017] As the state of the art in imaging systems advances and effortsare made to provide new imaging systems that can meet new performancerequirements, and to reduce or eliminate some of the undesirablecharacteristics of the known systems, it would be advantageous to havenew compounds which can be used as image-forming materials in imagingsystems, including thermal imaging systems.

SUMMARY OF THE INVENTION

[0018] It is therefore an object of this invention to provide novelcompounds.

[0019] Another object of the invention is to provide compounds whichexhibit different colors when in the crystalline form and in the liquidform.

[0020] Yet another object of the invention is to provide imaging membersand methods, including thermal imaging members and methods, whichutilize the novel compounds.

[0021] The present invention provides novel rhodamine compounds that areuseful as image dyes in imaging systems. According to one aspect of theinvention there are provided novel dye compounds which exhibit a firstcolor when in the crystalline form and a second color, different fromthe first color, when in the liquid, amorphous form.

[0022] In one embodiment of the invention there are provided novelcompounds which are represented by formula I

[0023] wherein:

[0024] R₁, R₃, R₄, R₅, R₆ and R₇ are each independently selected fromthe group consisting of hydrogen, alkyl, preferably having from 1 to 18carbon atoms, substituted alkyl, alkenyl, substituted alkenyl, alkynyl,substituted, alkynyl, heterocycloalkyl, substituted heterocycloalkyl,substituted carbonyl, acylamino, halogen, nitro, nitrilo, sulfonyl,aryl, substituted aryl, heteroaryl, substituted heteroaryl, oxygen,substituted oxygen, nitrogen, substituted nitrogen, sulfur andsubstituted sulfur;

[0025] R₂ is selected from the group consisting of hydrogen, alkyl,preferably having from 1 to 18 carbon atoms, substituted alkyl, alkenyl,substituted alkenyl, alkynyl, substituted alkynyl, heterocycloalkyl,substituted heterocycloalkyl, substituted carbonyl, sulfonyl, aryl,substituted aryl, heteroaryl, substituted heteroaryl, substitutedoxygen, substituted nitrogen and substituted sulfur;

[0026] R₈ is absent or selected from the group consisting of hydrogen,alkyl, preferably having from 1 to 18 carbon atoms, substituted alkyl,alkenyl, substituted alkenyl, alkynyl, substituted alkynyl,heterocycloalkyl, substituted heterocycloalkyl, substituted carbonyl,acylamino, halogen, nitro, nitrilo, sulfonyl, aryl, substituted aryl,heteroaryl, substituted heteroaryl, oxygen, substituted oxygen,nitrogen, substituted nitrogen, sulfur and substituted sulfur;

[0027] R₉, R₁₀ and R₁₁ are independently selected from the groupconsisting of hydrogen, alkyl, preferably having from 1 to 18 carbonatoms, substituted alkyl, alkenyl, substituted alkenyl, alkynyl,substituted alkynyl, heterocycloalkyl, substituted heterocycloalkyl,substituted carbonyl, acylamino, halogen, nitro, nitrilo, sulfonyl,aryl, substituted aryl, heteroaryl, substituted heteroaryl, oxygen,substituted oxygen, nitrogen, substituted nitrogen, sulfur andsubstituted sulfur;

[0028] R₁₂, R₁₃, R₁₄ and R₁₅ are independently selected from the groupconsisting of hydrogen, alkyl, preferably having from 1 to 18 carbonatoms, substituted alkyl, alkenyl, substituted alkenyl, alkynyl,substituted alkynyl, heterocycloalkyl, substituted heterocycloalkyl,substituted carbonyl, acylamino, aryl, substituted aryl, heteroaryl, andsubstituted heteroaryl;

[0029] R₁₆, R₁₇, R₁₈ and R₁₉ are independently selected from the groupconsisting of hydrogen, alkyl, preferably having from 1 to 18 carbonatoms, substituted alkyl, alkenyl, substituted alkenyl, alkynyl,substituted alkynyl, heterocycloalkyl, substituted heterocycloalkyl,substituted carbonyl, acylamino, halogen, nitro, nitrilo, sulfonyl,aryl, substituted aryl, heteroaryl, substituted heteroaryl, oxygen,substituted oxygen, nitrogen, substituted nitrogen, sulfur andsubstituted sulfur; and

[0030] X₁ is carbon or nitrogen.

[0031] In a preferred group of compounds represented by formula I, R₈,R₉, R₁₀ and R₁₁ are halogen and R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₁₂, R₁₃,R₁₄, R₁₅, R₁₆, R₁₇, R₁₈ and R₁₉ are as previously defined and X₁ iscarbon.

[0032] The conversion to the liquid form can be carried out by applyingheat to the compounds and therefore the compounds are useful in thermalimaging members used in thermal imaging methods. In such thermal imagingmethods thermal energy may be applied to the thermal imaging members byany of the techniques known in thermal imaging such as from a thermalprint head, a laser, a heated stylus, etc. In another embodiment, theconversion to the liquid form may be effected by applying a solvent forthe crystalline solid such as from an ink jet imaging apparatus to atleast partially dissolve the crystalline material. In anotherembodiment, one or more thermal solvents, which are crystallinematerials, can be incorporated in the thermal imaging member. Thecrystalline thermal solvent(s), upon being heated, melt and dissolve orliquefy, and thereby convert, at least partially, the crystallineimage-forming material to the liquid amorphous form to form the image.

[0033] The compounds of the invention may be incorporated in anysuitable thermal imaging members. Typical suitable thermal imagingmembers generally comprise a substrate carrying at least oneimage-forming layer including a compound in the crystalline form, whichcan be converted, at least partially to a liquid in the amorphous form,the liquid having intrinsically a different color from the crystallineform. The thermal imaging member may be monochrome or multicolor and thetemperature at which an image is formed in at least one of theimage-forming layers is time independent.

[0034] Preferred thermal imaging members according to the invention arethose having the structures described in prior co-pending commonlyassigned U.S. patent application Ser. No. 09/745,700 filed Dec. 20,2000, now U.S. Pat. No. 6,537,410 B1 which is hereby incorporated hereinby reference in its entirety and made a part of this application.

[0035] Other preferred thermal imaging members are those having thestructures described in prior, co-pending commonly assigned U.S. patentapplication Ser. No. 10/151,432 filed May 20, 2002 which is herebyincorporated herein by reference in its entirety and made a part of thisapplication.

[0036] Further preferred thermal imaging members are those having thestructures described in U.S. Pat. No. 6,054,246 which is herebyincorporated herein by reference in its entirety and made a part of thisapplication.

DETAILED DESCRIPTION OF THE INVENTION

[0037] Compounds in the crystalline state commonly have properties,including color, that are very different from those of the samecompounds in an amorphous form. In a crystal, a molecule is typicallyheld in a single conformation (or, more rarely, in a small number ofconformations) by the packing forces of the lattice. Likewise, if amolecule can exist in more than one interconverting isomeric forms, onlyone of such isomeric forms is commonly present in the crystalline state.In amorphous form or solution, on the other hand, the compound mayexplore its whole conformational and isomeric space, and only a smallproportion of the population of individual molecules of the compound mayat any one time exhibit the particular conformation or isomeric formadopted in the crystal. Compounds of the present invention exhibittautomerism in which at least one tautomeric form is colorless, and atleast another tautomeric form is colored. The crystalline form ofcompounds of the present invention comprises predominantly the colorlesstautomer.

[0038] A first embodiment of the invention is a compound represented byFormula I as described above.

[0039] A first embodiment of the invention is a compound whose colorlesstautomer is represented by formula I as described above.

[0040] Representative compounds according to the invention are those offormula I in which R₁, R₃, R₄, R₅, R₆, R₇, R₁₂, R₁₆, R₁₈ and R₁₉ arehydrogen, X₁ is carbon, and the other substituents are as shown in TableI: TABLE I Com- R₈, R₉, R₁₃, pound R₂ R₁₀, R₁₁ R₁₄, R₁₅ R₁₇ I C₆H₅ Cl MeH II 4-(O-2-ethyl-1-hexyl)C₆H₄ Cl H H III 3,4-dioctyloxy-C₆H₃ Cl H H IV4-(2-hydroxy-1-decyloxy)-C₆H₄ Cl H H V 3,4-dioctyloxy-C₆H₃ Cl H OMe VI2-isopropyl-C₆H₄ F H H VII 2-Methyl-4-decyloxy-C₆H₃ F H H VIII2-Methyl-4-decyloxy-C₆H₃ F H Me IX 2-Methyl-4-octadecyloxy-C₆H₃ F H H

[0041] Preferred compounds according to the invention are III, VII andVIII.

[0042] Definitions

[0043] The term “alkyl” as used herein refers to saturatedstraight-chain, branched-chain or cyclic hydrocarbon radicals. Examplesof alkyl radicals include, but are not limited to, methyl, ethyl,propyl, isopropyl, n-butyl, tert-butyl, neopentyl, n-hexyl, cyclohexyl,n-octyl, n-decyl, n-dodecyl and n-hexadecyl radicals.

[0044] The term “alkenyl” as used herein refers to unsaturatedstraight-chain, branched-chain or cyclic hydrocarbon radicals. Examplesof alkenyl radicals include, but are not limited to, allyl, butenyl,hexenyl and cyclohexenyl radicals.

[0045] The term “alkynyl” as used herein refers to unsaturatedhydrocarbon radicals having at least one carbon-carbon triple bond.Representative alkynyl groups include, but are not limited to, ethynyl,1-propynyl, 1-butynyl, isopentynyl, 1,3-hexadiynyl, n-hexynyl,3-pentynyl, 1-hexen-3-ynyl and the like.

[0046] The terms “halo” and “halogen,” as used herein, refer to an atomselected from fluorine, chlorine, bromine and iodine.

[0047] The term “aryl,” as used herein, refers to a mono-, bicyclic ortricyclic carbocyclic ring system having one, two or three aromaticrings including, but not limited to, phenyl, naphthyl, anthryl, azulyl,tetrahydronaphthyl, indanyl, indenyl and the like.

[0048] The term “heteroaryl,” as used herein, refers to a cyclicaromatic radical having from five to ten ring atoms of which one ringatom is selected from S, O and N; zero, one or two ring atoms areadditional heteroatoms independently selected from S, O and N; and theremaining ring atoms are carbon, the radical being joined to the rest ofthe molecule via any of the ring atoms, such as, for example, pyridinyl,pyrazinyl, pyrimidinyl, pyrrolyl, pyrazolyl, imidazolyl, thiazolyl,oxazolyl, isooxazolyl, thiadiazolyl, oxadiazolyl, thiophenyl, furanyl,quinolinyl, isoquinolinyl, and the like.

[0049] The term “heterocycloalkyl,” as used herein, refers to anon-aromatic 3-, 4-, 5-, 6- or 7-membered ring or a bi- or tri-cyclicgroup comprising fused six-membered rings having between one and threeheteroatoms independently selected from oxygen, sulfur and nitrogen,wherein (i) each 5-membered ring has 0 to 1 double bonds and each6-membered ring has 0 to 2 double bonds, (ii) the nitrogen and sulfurheteroatoms may optionally be oxidized, (iii) the nitrogen heteroatommay optionally be quaternized, and (iv) any of the above heterocyclicrings may be fused to a benzene ring. Representative heterocyclesinclude, but are not limited to, pyrrolidinyl, pyrazolinyl,pyrazolidinyl, imidazolinyl, imidazolidinyl, piperidinyl, piperazinyl,oxazolidinyl, isoxazolidinyl, morpholinyl, thiazolidinyl,isothiazolidinyl, and tetrahydrofuryl.

[0050] The term “carbonyl” as used herein refers to a carbonyl group,attached to the parent molecular moiety through the carbon atom, thiscarbon atom also bearing a hydrogen atom, or in the case of a“substituted carbonyl” a substituent as described in the definition of“substituted” below.

[0051] The term “acyl” as used herein refers to groups containing acarbonyl moiety. Examples of acyl radicals include, but are not limitedto, formyl, acetyl, propionyl, benzoyl and naphthyl.

[0052] The term “alkoxy”, as used herein, refers to a substituted orunsubstituted alkyl, alkenyl or heterocycloalkyl group, as previouslydefined, attached to the parent molecular moiety through an oxygen atom.Examples of alkoxy radicals include, but are not limited to, methoxy,ethoxy, propoxy, isopropoxy, n-butoxy, tert-butoxy, neopentoxy andn-hexoxy.

[0053] The term ‘aryloxy” as used herein refers to a substituted orunsubstituted aryl or heteroaryl group, as previously defined, attachedto the parent molecular moiety through an oxygen atom. Examples ofaryloxy include, but are not limited to, phenoxy, p-methylphenoxy,naphthoxy and the like.

[0054] The term “alkylamino”, as used herein, refers to a substituted orunsubstituted alkyl, alkenyl or heterocycloalkyl group, as previouslydefined, attached to the parent molecular moiety through a nitrogenatom. Examples of alkylamino radicals include, but are not limited to,methylamino, ethylamino, hexylaminoand dodecylamino.

[0055] The term “arylamino”, as used herein, refers to a substituted orunsubstituted aryl or heteroaryl group, as previously defined, attachedto the parent molecular moiety through a nitrogen atom.

[0056] The term “substituted” as used herein in phrases such as“substituted alkyl”, “substituted alkenyl”, “substituted aryl”,“substituted heteroaryl”, “substituted heterocycloalkyl”, “substitutedcarbonyl”, “substituted alkoxy”, “substituted acyl”, “substitutedamino”, “substituted aryloxy”, and the like, refers to independentreplacement of one or more of the hydrogen atoms on the substitutedmoiety with substituents independently selected from, but not limitedto, alkyl, alkenyl, heterocycloalkyl, alkoxy, aryloxy, hydroxy, amino,alkylamino, arylamino, cyano, halo, mercapto, nitro, carbonyl, acyl,aryl and heteroaryl groups.

[0057] According to the invention, there have been provided moleculesexhibiting tautomerism in which at least one tautomeric form iscolorless, and at least another tautomeric form is colored.Crystallization of the equilibrating mixture of the two tautomeric formsis carried out so as to produce colorless crystals. The solvent chosento perform the crystallization will typically be one of such polarity(and other chemical properties, such as hydrogen-bonding ability) thatthe pure colorless crystal form is favored, either in the equilibriumbetween the colorless and colored forms in solution, or in having lowersolubility in the solvent than the colored form. The choice of solventis usually determined empirically for a particular mixture of tautomers.

[0058] Upon conversion of the pure crystalline colorless form, theequilibrium between the two tautomers is re-established in the resultingamorphous (liquid) phase. The proportion of the amorphous material thatis colored (i.e., the proportion that is in the colored tautomeric form)may vary, but is preferably at least about 10%.

[0059] The colored and colorless tautomeric forms of the molecules ofthe present invention must meet certain criteria for image quality andpermanence. The colorless form, which is preferably the crystallineform, should have minimal visible absorption. It should be stable tolight, heating below the melting point, humidity, and otherenvironmental factors such as ozone, oxygen, nitrogen oxides,fingerprint oils, etc. These environmental factors are well known tothose skilled in the imaging art. The colored, amorphous form should bestable also to the above mentioned conditions, and in addition shouldnot recrystallize to the colorless form under normal handling conditionsof the image. The colored form should have a spectral absorptionappropriate for digital color rendition. Typically, the colored formshould be yellow (blue-absorbing), magenta (green-absorbing), cyan (redabsorbing), or black, without undue absorption in an unintended spectralregion. For nonphotographic applications, however, it may be requiredthat the colored form not be one of the subtractive primary colors, butrather a particular spot color (for example, orange, blue, etc.).

[0060] The compounds of the invention may be prepared by syntheticprocesses which are known to those skilled in the art, particularly inview of the state of the art and the specific preparatory examplesprovided below herein.

[0061] Symmetrical rhodamine dyes can be prepared in one step from3′,6′-dichlorofluorans by reacting two equivalents of an aromatic oraliphatic amine as described in U.S. Pat. No. 4,602,263, British PatentNo. GB2311075 and German Patent No. DE81056. The novel unsymmetricalrhodamine dyes in this application require a more controlled syntheticpathway in which one equivalent of an indoline is reacted selectivelywith the 3′,6′-dichlorofluoran using aluminum chloride as a catalyst toproduce 3′-chloro-6′-indolinofluorans. These products are isolated andpurified prior to reacting with a second equivalent of an aromatic oraliphatic amine. Zinc chloride is used as the catalyst for the secondaddition. German Patent No. DE139727 describes the selective addition ofanilines to 3′,6′-dichlorofluorans to produce3′-chloro-6′-arylaminofluorans using a mixture of zinc chloride and zincoxide at 160° C.

[0062] To optimize the chromophore, melting point, degree of coloration,light stability and solubility of the dyes in this application a varietyof indolines, anilines and dichlorofluorans are utilized.

[0063] 5-methoxyindoline and 5-methylindoline are prepared from thecorresponding indoles by reduction with sodium cyanoborohydride inacetic acid. 2,3,3-trimethylindoline is prepared from2,3,3-trimethylindolenine by hydrogenation.

[0064] The aromatic amines used in this application are synthesized from4-nitro-3-methylphenol, 4-nitrophenol and 4-nitrocatechol. The anions ofthe phenols are generated in dimethylformamide with potassium carbonateand alkylated with a variety of alkylating agents such as 1-bromodecane,1-bromooctadecane, 1-bromo-2-ethylhexane. Alternatively, the sodiumsalts of the phenols are alkylated with 1,2-epoxyalkanes usingtetrabutylammonium sulfate in a boiling mixture of toluene and water.The resulting 4-nitrophenylethers are reduced to the correspondinganilines using standard methods such as hydrogenation, iron powder,hydrazine or ammonium formate.

[0065] The 3′,6′-dichlorofluorans are synthesized from the correspondingfluoresceins using thionyl chloride and dimethylformamide in a variationof the method of Hurd described in the Journal of the Amer. ChemicalSoc. 59, 112 (1937). 4,5,6,7-tetrafluorofluorescein is preparedaccording to the procedure of Haugland described in the Journal ofOrganic Chemistry, 62, 6469 (1997).

[0066] The thermal imaging members of the invention can be directthermal imaging members wherein an image is formed in the member itselfor they can be thermal transfer imaging members whereby image-formingmaterial is transferred to an image-receiving member. The melting pointof the molecules used in direct thermal imaging members of the presentinvention is preferably in the range of about 60° C. to about 300° C.Melting points lower than about 60° C. lead to direct thermal imagingmembers that are unstable to temperatures occasionally encounteredduring handling of the members before or after imaging, while meltingtemperatures above about 300° C. render the compounds difficult tocolorize with a conventional thermal print head. It should be noted,however, that there are uses for certain novel compounds of the presentinvention that do not require the use of thermal print heads (forexample, laser imaging).

[0067] The colors formed by preferred compounds of the present inventionare typically cyan, which is to say that the maximum absorption of thepreferred compounds in the amorphous state lies between about 600 andabout 700 nm. It has been found that the wavelength of maximumabsorption of the colored form of compounds of the present invention islonger when substituents R₈, R₉, R₁₀ and R₁₁ of formula I areelectron-withdrawing relative to hydrogen. Dyes with relatively shortmaximum absorption wavelengths may appear blue, rather than cyan, andfor this reason substituents R₈, R₉, R₁₀ and R₁₁ of formula I arepreferred to be highly electron-withdrawing, and preferably halogen,when X₁ of formula I is a carbon atom and the color cyan is desired.

[0068] To form a direct thermal imaging system, the crystalline,colorless form of the compounds of the invention is made into adispersion in a solvent in which the compound is insoluble or onlysparingly soluble, by any of the methods known in the art for formingdispersions. Such methods include grinding, attriting, etc. Theparticular solvent chosen will depend upon the particular crystallinematerial. Solvents that may be used include water, organic solvents suchas hydrocarbons, esters, alcohols, ketones, nitrites, and organic halidesolvents such as chlorinated and fluorinated hydrocarbons. The dispersedcrystalline material may be combined with a binder, which may bepolymeric. Suitable binders include water-soluble polymers such aspoly(vinyl alcohol), poly(vinylpyrollidone) and cellulose derivatives,water-dispersed latices such as styrene/butadiene or poly(urethane)derivatives, or alternatively hydrocarbon-soluble polymers such aspolyethylene, polypropylene, copolymers of ethylene and norbornene, andpolystyrene. This list is not intended to be exhaustive, but is merelyintended to indicate the breadth of choice available for the polymericbinder. The binder may be dissolved or dispersed in the solvent.

[0069] Following preparation of the dispersion of the compound of thepresent invention, and optional addition of a polymeric binder, theresultant fluid is coated onto a substrate using any of the techniqueswell-known in the coating art. These include slot, gravure, Meyer rod,roll, cascade, spray, and curtain coating techniques. The image-forminglayer so formed is optionally overcoated with a protective layer orlayers.

[0070] If materials of the present invention are used to prepare animaging medium of the type described in copending U.S. patentapplication Ser. No. 10/151,432 filed May 20, 2002 the process describedabove is followed for each of the imaging layers. Successive layers maybe coated sequentially, in tandem, or in a combination of sequential andtandem coatings.

EXAMPLES

[0071] The invention will now be described further in detail withrespect to specific embodiments by way of examples, it being understoodthat these are intended to be illustrative only and the invention is notlimited to the materials, amounts, procedures and process parameters,etc. recited therein. All parts and percentages recited are by weightunless otherwise specified.

Example 1 Synthesis of intermediates Step 1A. Alkylation of4-nitrocatechol

[0072] 4-Nitrocatechol (23.26 g, 0.15 mol) and potassium carbonate(124.38 g, 0.9 mol) were placed in a one liter 3-neck flask fitted witha mechanical stirrer. Anhydrous dimethylformamide (350 mL) was added tothis mixture followed by the addition to the suspension, dropwise, of1-bromo octane (63.73 g, 0.33 mol). The reaction mixture was heated at110° C. for 24 hours. The reaction was followed by TLC (2% methanol inmethylene chloride). After the completion of the reaction the contentswere cooled and poured dropwise with stirring into ice-water (1 L). Themixture was stirred for one hour and filtered. The collected solid waswashed thoroughly with water, air-dried and then dried in vacuo at 30°C. This process produced brown crystals: (54.8 g, 0.144 mol, 96% yield).These crystals were used without further purification.

Step 1B. Synthesis of 3,4-dioctyloxyaniline

[0073] 3,4-Dioctyloxynitrobenzene (25.25 g, 0.067 mol) was dissolved inethyl acetate (250 mL) in a Parr bottle. 10% Pd on charcoal (3.5 g) wasadded and the mixture was hydrogenated (5-6 hr) at 50 psi until thehydrogen uptake ceased. The reaction mixture was filtered andevaporated. The aniline was obtained as a dark syrup. (22.5 g, 0.064mol, 97% yield).

[0074] The structure was corroborated by NMR and mass spectroscopy.

Step 1C. Synthesis of 2-methyl-4-decyloxynitro benzene

[0075] To a solution of 3-methyl-4-nitrophenol (45 g, 0.294 mol) indimethylformamide (270 mL) there were added 1-bromodecane (65 g, 0.294mol) and potassium carbonate (121.8 g, 0.882 mol). The reaction mixturewas heated to 115° C. and stirred at that temperature for 48 hours. Thereaction mixture was cooled and poured into water (4L), stirred for 0.5hour and extracted with two portions of ethyl acetate (1.5L and 600 mL).The combined organic extracts were washed with 5% aqueous solutionsodium bicarbonate (1L), water (1L and 0.5L), dried over sodium sulfateand concentrated to give the crude product (90 g, 0.294 mol, 100%yield). This product was used in the next step without purification.

Step 1D. Synthesis of 2-methyl-4-decyloxyaniline

[0076] The mixture of crude 2-methyl-4-decyloxynitrobenzene (90 g, 0.294mol), methanol (246 mL), concentrated hydrochloric acid (159 mL) anddioxane (70 mL) was heated to 75° C. Iron powder (49.9 g, 0.89 mol) wasadded in small portions with vigorous stirring. After the addition wascomplete the reaction mixture was stirred at 75° C. for another 20minutes and poured warm into water (3L), stirred for 30 minutes and thepH adjusted to 11.0 by addition of aqueous potassium carbonate solution.Dichloromethane (3L) was added and the mixture was stirred intensivelyfor 1 hour. The layers were separated and the organic layer dried oversodium sulfate and passed through a thin pad of silica gel. The solventwas evaporated to dryness to give a brown oil (58.5 g, 0.22 mol, 76%yield).

Step 1E. Synthesis of 2-methyl-4-octadecyloxynitrobenzene

[0077] 1-Bromooctadecane (43.54 g, 0.131 mol) and potassium carbonate(54.15 g, 0.392 mol) were added to a solution of 3-methyl-4-nitrophenol(20 g, 0.131 mol) in dimethylformamide (120 mL) The reaction mixture washeated to 110° C. and stirred at this temperature for 60 hours. Thereaction mixture was cooled and poured into water (2L), stirred for 0.5hour and extracted with methylene chloride (1L). The organic extract waswashed with 5% aqueous solution sodium bicarbonate (0.5L), water(2×0.6L), dried over sodium sulfate and concentrated to give (60 g) ofcrude product. This product was used in the next step withoutpurification.

Step 1F. Synthesis of 2-methyl-4-octadecyloxyaniline

[0078] The mixture of crude 2-methyl-4-octadecyloxynitrobenzene (30 g,ca. 0.065 mol), methanol (55 mL), concentrated hydrochloric acid (40.5mL) and dioxane (50 mL) was heated to 85° C. Iron powder (11.2 g, 0.20mol) was added in small portions with intensive stirring. After theaddition was complete the reaction mixture was stirred at 85° C. foranother 3 hours and poured warm into water (800 mL), stirred for 30minutes and the pH adjusted to 10.0 by addition of aqueous potassiumcarbonate solution. Dichloromethane (1.0L) was added and mixture wasstirred intensively for 1 hour. The layers were separated and theorganic layer was washed with water (2×500 mL) and dried over sodiumsulfate. The solvent was evaporated to give an oil (20 g, 0.053 mol, 82%yield), which solidified on standing.

[0079] The structure of this material was corroborated by proton NMR andmass spectroscopy.

Step 1G. Synthesis of 2-ethyl-1-hexyloxynitro benzene

[0080] 4-Nitrophenol (10 g, 72 mmol) and potassium carbonate (30.4 g,0.22 mol) were added to dimethylformamide (80 mL) at room temperatureand the mixture was stirred with heating at 100° C. for 2 hours.2-Ethyl-1-hexyl bromide (16.7 g, 86 mmol) was slowly added to themixture for 20 minutes. After the addition the mixture was furtherstirred at 150° C. for 3 hours. After cooling, the reaction mixture waspoured into water (500 mL) and then the mixture was extracted withmethylene chloride. After evaporation of solvent, the residual productwas isolated as an oil in high yield (18 g, 71.6 mmol, 99% yield).

Step 1H. Synthesis of 2-ethyl-1-hexyloxy aniline

[0081] 2-Ethyl-1-hexyloxynitro benzene (18 g, 72 mmol) was dissolved inisopropanol (80 mL) and 10% Pd/C (1 g) was slowly added to the mixturein a Parr pressure bottle. The mixture was hydrogenated at 40 psi for 5hours and the mixture was filtered to remove Pd/C followed byevaporation of the solvent to give the oily product in quantitativeyield (15.9 g, 72 mmol, 100% yield).

Step 1I. Synthesis of 4-(2-hydroxy-1-decyloxy)nitrobenzene

[0082] The sodium salt of 4-nitrophenol (28.19 g, 0.175 mol) wasdissolved in water (50 mL) and toluene (300 mL) and tetrabutylammoniumsulfate (6.0 g) was added. 1,2-Epoxydecane (27.3 g, 0.175 mol) was addedto this mixture and the reaction was heated at 100° C. for 5 days. Thetoluene layer was separated and washed with water (4×75 mL), 1Nhydrochloric acid (2×75 mL) and water (75 mL). The organic layer wasdried over sodium sulfate, filtered and the solvent removed. The crudeproduct was purified by silica gel chromatography (2-3%methanol/methylene chloride) to afford4-(2-hydroxy-1-decyloxy)nitrobenzene as a pale oil (20 g, 0.68 mol, 39%yield).

Step 1J. Synthesis of 4-(2-hydroxy-1-decyloxy)aniline

[0083] 4-(2-hydroxy-1-decyloxy)nitrobenzene (20 g, 0.68 mol) wasdissolved in ethyl acetate (200 mL) and 10% palladium on carbon (2.5 g)was added to a Parr pressure bottle. The contents were then hydrogenatedat 50 psi until hydrogen uptake ceased. The catalyst was removed bysuction filtration through a pad of Celite. Removal of solvent afforded4-(2-hydroxy-1-decyloxy)aniline in quantitative yield (18.0 g, 0.68 mol,100% yield) as a tan solid.

[0084] The structure was confirmed by NMR and mass spectroscopy.

Step 1K. Synthesis of 5-methoxyindoline

[0085] 5-Methoxyindole (50 g, 0.34 mol) was dissolved in glacial aceticacid (500 mL) in a 3L 3-necked flask fitted with a mechanical stirrer, adropping funnel and a thermometer. The solution was cooled to 10-12° C.with an ice bath and sodium cyanoborohydride (64 g, 1.0 mol) was addedin portions while ensuring the temperature remained at or below 15-16°C. After the addition was complete the cooling bath was removed and thereaction was warmed to ambient temperature for 0.5 hour. TLC (1:1EtOAc/hexane) confirmed a complete reaction. The reaction was cooled to5-10° C. and 50% aqueous sodium hydroxide was added until the pH was8-10. The product oiled out and was extracted with ethyl acetate (3×700mL). The combined organic layers were washed with water (2×500 mL) andbrine (400 mL), dried over anhydrous potassium carbonate, filtered andconcentrated to afford 5-methoxyindoline (50 g, 0.337 mol, 99% yield) asa thick oil. This product was used without further purification.

[0086] The structure was corroborated by NMR spectroscopy.

Step 1L. Synthesis of 5-methylindoline

[0087] 5-Methylindoline was prepared from 5-methylindole using theprocedure described for the preparation of 5-methoxyindoline.5-Methylindole (11 g, 0.0835 mol) in glacial acetic acid (150 mL) in a1L 3-necked flask was reduced at 10-15° C. with sodium cyanoborohydride(15.8 g, 0.251 mol). Extraction with ethyl acetate provided5-methylindoline (11 g, 0.0832 mol, 99% yield) as a thick oil which wasused without further purification.

[0088] The structure was corroborated by NMR spectroscopy.

Step 1M. Synthesis of 3′,6′,4,5,6,7-hexachlorofluoran

[0089] Acetonitrile (680 mL), dimethylformamide (7 mL),tetrachlorofluorescein (170 g, 0.36 mol) and thionyl chloride (215 g,1.8 mol) were added to a 3-liter 3-neck round bottom flask fitted with amechanical stirrer, condenser and nitrogen inlet tube. Upon heating, asolution was briefly obtained followed by gradual crystallization of theproduct. The mixture was further heated at reflux (72° C.) for sixhours. After cooling to room temperature, water (100 mL) was slowly andcarefully added. The product was filtered and washed well withacetonitrile. Air drying provided a pale violet solid (141.5 g, 0.279mol, 77% yield). The crude product was stirred in dimethylformamide (425mL), heated to 100° C., and allowed to stand overnight. The pale violetcrystals were filtered, washed with dimethylformamide followed bymethanol and dried under vacuum at 60° C. to provide hexachlorofluoran(98.7 g, 0.195 mol, 54% yield).

[0090] Assay by HPLC was 97% by area.

Step 1N. Synthesis of 3′-indolino-6′,4,5,6,7-pentachlorofluoran

[0091] Hexachlorofluoran (5.07 g, 10 mmol), 2,6-lutidine (1.07 g, 10mmol), aluminum chloride (9.33 g, 70 mmol) and sulfolane (50 mL) wereadded to a 100 mL 3-neck round bottom flask fitted with a mechanicalstirrer, condenser, thermometer and nitrogen inlet tube. The mixture washeated to 100° C. and indoline (1.19 g, 10 mmol) was added. Thetemperature was raised to 180° C. and heating continued for 6 hours.After cooling to room temperature, the mixture was poured into coldwater (250 mL) with rapid agitation. The blue-gray solid was filtered,washed with water and air-dried providing the crude product (5 g). Thecrude product was stirred in dimethylformamide (20 mL), heated to 100°C. and allowed to stand overnight. The resulting pale green solid wasfiltered, washed first with dimethylformamide followed by methanol anddried under vacuum at 60° C. to provide 3-indolinopentachlorofluoran(3.60 g, 6.1 mmol, 61% yeld). Assay by HPLC was 97% by area.

Step 1P. Synthesis OF3′-(5-methoxyindolino)-6′,4,5,6,7-pentachlorofluoran

[0092] Hexachlorofluoran (20 g, 0.0394 mol), aluminum chloride (20.8 g,0.156 mol) and sulfolane (100 g) were added to a 250 mL 3-neck roundbottom flask fitted with a mechanical stirrer, condenser, thermometerand nitrogen inlet tube. The mixture was heated to 120° C. and5-methoxyindoline (12 g, 0.081 mol) was added. The reaction mixture washeated overnight at 120° C. After cooling to room temperature, themixture was poured into cold water (1L) with rapid agitation. The solidwas filtered, washed with water and air-dried for several days followedby vacuum drying at 70° C. to give the crude product (25.5 g, 0.041 mol,104% yield) which was used without further purification.

Step 1Q. Synthesis of 4,5,6,7-tetrafluorofluorescein

[0093] Using a mechanical stirrer, tetrafluorophthalic anhydride (50 g,0.227 mol) was dissolved in methanesulfonic acid (221 mL). The anhydridedissolved completely as the temperature reached 40° C. When thetemperature had reached 120° C., resorcinol (62.3 g, 0.568 mol) wasadded in 3 portions giving enough time between additions for thematerial to go into solution. The solution turned pale red. An HPLC ofthe reaction mixture was taken at the start of the reaction and everyhour thereafter. The reaction was complete after three hours. Heatingwas stopped and the reaction mixture was allowed to cool to ambienttemperature. The dark semi-solid residue was slowly poured into rapidlystirred ice water (2L). A fine, olive-green solid precipitated in thewater. The solid suspension was extracted with ethyl acetate (1L)followed by further extractions with ethyl acetate (4×400 mL). Theorganic fractions were combined and dried over anhydrous magnesiumsulfate (250 g). After stirring overnight, the drying agent was removedby vacuum filtration through a Celite pad. The ethyl acetate was removedon a rotary evaporator to give a dark brown-black solid (95 g) that wasnot further purified. The solid was dried in a vacuum desiccatorovernight at 70° C.

Step 1R. Synthesis of 3′,6′-Dichloro-4,5,6,7-tetrafluoran

[0094] Using a mechanical stirrer, tetrafluorofluorescein (95 g, ca.0.235 mol) was suspended in a mixture of acetonitrile (350 mL) anddimethylformamide (5.8 mL). Thionyl chloride (79 mL, 129.3 g, 1.08 mol)was added to this mixture. The reaction mixture was heated to reflux for4 hours. HPLC showed complete conversion after 4 hours. The excessacetonitrile and excess thionyl chloride were removed by distillation ina stream of nitrogen. When nearly all of the solvent had been removed,the solid was resuspended in a solution of acetonitrile/water (95:5).The violet-brown solid was collected by vacuum filtration, washed with95:5 acetonitrile/water (500 mL) followed by drying in a vacuumdesiccator at 70° C. for 4 hours to give the desired product (84 g, 0.19mol, 80% yield).

Step 1S. Synthesis of 3′-indolino-6′chloro-4,5,6,7-tetrafluorofluoran

[0095] 3′,6′-Dichloro-4,5,6,7-tetrafluorofloran (20 g, 0.045 mol),2,6-lutidine (4.74 g, 0.045 mol) and sulfolane (56 mL) were added to a250 mL 3-neck round bottom flask fitted with a mechanical stirrer.Aluminum chloride (40.2 g, 0.28 mol) was added in small portions and theresulting mixture was stirred for 20 minutes. The temperature rose to110° C. Indoline (5.13 g, 0.045 mol) was added slowly followed by2,6-lutidine (4.74 g, 0.045 mol) and the reaction was heated at 110° C.for 5 hours. The reaction was followed to completion by HPLC. Thereaction was poured into a mixture of crushed ice and water withvigorous agitation. The dark blue solid was collected by suctionfiltration, washed with water and dried under vacuum. The crude productwas passed through a silica gel plug (300 g) using methylene chloride toelute. Removal of solvent provided the indolinofluoran as a yellow-greenfoam (16 g, 0.031 mol, 68% yield).

[0096] The structure was confirmed by NMR and mass spectroscopy.

Step 1T. Synthesis of3′-(5-methylindolino)-6′chloro-4,5,6,7-tetrafluorofluoran

[0097] 3′,6′-Dichloro-4,5,6,7-tetrafluorofluoran (13.23 g, 0.030 mol),2,6-lutidine (6.43 g, 0.060 mol) and sulfolane (30Ml) were added to a100 mL 3-neck round bottom flask fitted with a condenser. Aluminumchloride (16 g, 0.120 mol) was added followed by 5-methylindoline (4.0g, 0.030 mol) and the reaction was heated at 110-120° C. for 20 hoursunder nitrogen. The reaction mixture was poured into a mixture ofcrushed ice, water, and hydrochloric acid (500 mL) with vigorousagitation and stirred for 0.5 hour. The solid was dissolved in ethylacetate and washed with 10% sodium bicarbonate solution. The organiclayer was separated, dried over sodium sulfate and concentrated Thecrude product was passed through a short column of silica gel usingmethylene chloride to elute. Removal of solvent provided the3′-(5-methylindolino)-6′-chloro-4,5,6,7-tetraflourofluoran as a solid(4.6 g, 8.5 mmol, 28% yield).

[0098] The structure was confirmed by NMR and mass spectroscopy.

Example II Synthesis of Dye I

[0099] A mixture of hexachlorofluoran (2.0 g, 3.9 mmol),2,3,3-trimethylindoline (0.9 g; 5.9 mmol), zinc chloride (1.6 g; 11.8mmol), and zinc oxide (0.5 g; 5.9 mol) in sulfolane (6 g) was stirredwith heating at 190° C. for 4 hours. To this mixture was added aniline(0.8 g; 7.9 mmol) and the mixture was then further stirred with heatingat 160° C. for 14 hours. The mixture was cooled to 50° C. and quenchedinto 2N HCl (100 mL). The crude solid was isolated by filtration, washedwith water several times and taken up in methylene chloride (150 mL).The methylene chloride solution was washed with sat. sodium bicarbonate(2×100 mL), dried over magnesium sulfate and the solvent removed. Theresidual solid was purified by column chromatography on silica gel(eluted with 30% ethyl acetate in hexane) to give 0.6 g pure product(22% yield) and then recrystallized from ca. 10% acetone in hexane togive colorless crystalline product, m.p. 210-215° C. (0.35 g, 13%yield).

[0100] The structure was confirmed by proton NMR and mass spectroscopy.

Example III Synthesis of Dye II

[0101] A mixture of hexachlorofluoran (2.0 g, 3.9 mmol), indoline (0.7g, 5.9 mmol), zinc chloride (1.6 g, 11.8 mmol), and zinc oxide (0.5 g,5.9 mmol) in sulfolane (6 g) was stirred with heating at 145° C. for 90minutes. To this mixture was added 4-(2-ethyl-1-hexyloxy) aniline (2.7g, 7.9 mmol) and the mixture was further stirred with heating at 160° C.for 5 hours. The mixture was cooled to 50° C. and quenched into 2N HCl(100 mL). The crude solid was isolated by filtration, washed with waterseveral times and taken up in methylene chloride (150 mL). The methylenechloride solution was washed with sat. sodium bicarbonate (2×100 mL),dried over magnesium sulfate and the solvent was evaporated. Theresidual solid was purified by column chromatography (10% ethyl acetatein methylene chloride) to give 1.2 g pure product (39% yield) andrecrystallized from approximately 10% acetone/hexane to give colorlesscrystalline product (0.55 g, m.p. 180-182° C., 18% yield).

[0102] The structure was confirmed by proton NMR and mass spectroscopy.

Example IV Synthesis of Dye III

[0103] Pentachloroindolinofluoran (11.8 g, 20 mmol), ZnCl₂ (8.2 g, 60mmol) and ZnO (2.43 g, 30 mmol) were added to a 250 ml round bottomflask containing sulfolane (30 g) and the flask warmed to dissolve thesolids. To the hot blue solution was added 3,4-dioctyloxyaniline (13.96g, 40 mmol) and the flask was placed with an air condenser into an oilbath preheated to 140° C. The reaction mixture was stirred at thattemperature for 2 hours. The reaction was followed by TLC (25% ethylacetate in hexane) until complete. The reaction mixture was cooled and2N HCl (400 mL) was added followed by trituration with a spatula tobreak the large blue mass to a crystalline powder. The reaction mixturewas filtered and washed copiously with water. The crude product wasdissolved in ethyl acetate (1200 mL) and extracted with 10% Na₂CO₃(2×250 mL), followed by water and brine (250 mL each). The organic layerwas dried over sodium sulfate and evaporated to yield crude blue product(23 g).

[0104] The crude product was purified on a silica gel column (1.5 Kg)packed in methylene chloride. The product was eluted with 10% ethylacetate/methylene chloride (5L). Pure fractions were pooled to obtainthe product as a glass (13.5 g) which was crystallized from 10% acetonein hexane to obtain a first crop of colorless crystals (8.5 g, 9.4 mmol,47% yield). Recrystallization of the mother liquor provided a secondcrop of crystals (2.5 g, 2.7 mmol, 13.5% yield). The overall yield was11.0 g, 12.1 mmol, 60.5% yield.

[0105] NMR analysis and mass spectroscopy confirmed the structure.

Example V Synthesis of Dye IV

[0106] 3′-Indolinopentachlorofluorescin (2.15 g, 3.6 mmol),4-(2-hydroxy-1-decyloxy)aniline (1.81 g, 6.8 mmol), zinc chloride (1.5g, 11 mmol), zinc oxide (0.45 g, 5.6 mmol) and tetramethylene sulfone (8g) were added to a 100-mL flask. The reaction mixture was heated at 150°C. for 12 hours under an atmosphere of nitrogen. The cooled mixture waspoured into 2N hydrochloric acid (100 mL). A dark blue precipitate wasobtained and filtered and washed with 0.5N aq. hydrochloric acidsolution (100 mL) and water (100 mL). The crude product was purified bysilica gel column chromatography (loaded and eluted with 500 ml ofmethylene chloride, followed by 500 ml of 1% methanol/methylenechloride). The solvent was removed by rotary evaporation to collect adark blue powder (2.3 g, 2.77 mmol, 77% yield). Pale greenish crystalswere obtained by recrystallization from 10% acetone/hexanes. m.p:156-158° C.

[0107] The structure was confirmed by proton NMR and mass spectroscopy.

Example VI Synthesis of Dye V

[0108] A mixture of hexachlorofluoran (1.0 g, 1.9 mmol),5-methoxyindoline (0.5 g, 3.0 mmol), zinc chloride (0.8 g, 5.9 mmol),and zinc oxide (0.3 g, 2.5 mmol) in sulfolane (4 g) was stirred withheating at 145° C. for 2 hours. To this mixture was added3,4-dioctyloxyaniline (1.4 g, 4.0 mmol) and the mixture was furtherstirred with heating at 160° C. for 5 hours. The mixture was cooled to50° C. and quenched into 2N HCl (100 mL). The crude solid was isolatedby filtration, washed with water several times and taken up in methylenechloride (150 mL). The methylene chloride solution was washed with sat.sodium bicarbonate (2×100 mL), dried over magnesium sulfate and thesolvent was removed. The residual solid was purified by columnchromatography on silica gel eluted with 20% ethyl acetate in methylenechloride to give pure product (0.80 g, 0.836 mmol, 44% yield) which wasrecrystallized from acetonitrile to give colorless crystalline product(0.35 g, 0.836 mmol, 19% yield) m.p. 117-119° C.

[0109] The structure was confirmed by proton NMR and mass spectroscopy.

Example VII Synthesis of Dye VI

[0110] A mixture of 3′-indolino-6′-chloro-4,5,6,7-tetrafluorofloran (1.0g, 1.9 mmol), zinc chloride (0.8 g, 5.7 mmol), zinc oxide (0.2 g, 2.8mmol), and 2-isopropylanilne (0.5 g, 3.8 mmol) in sulfolane (4 g) wasstirred with heating at 160° C. for 14 hours. The mixture was cooled to50° C. and quenched into 2N HCl (100 mL). The crude solid was isolatedby filtration, washed with water several times and taken up in methylenechloride (150 mL). This methylene chloride solution was washed with sat.sodium bicarbonate (2×100 mL), and dried over magnesium sulfate toremove the solvent. he residual solid was purified by columnchromatography on silica gel eluted with 35% ethyl acetate in methylenechloride to give pure product (0.60 g, 0.95 mmol, 50% yield) which wasrecrystallized from 10% acetone in hexane to give colorless crystallineproduct (0.3 g, 0.475 mmol, 25% yield) m.p.209-210° C.

[0111] The structure was confirmed by proton NMR and mass spectroscopy.

Example VIII Synthesis of Dye VII

[0112] A mixture of 3′-indolino-6′-chloro-4,5,6,7-tetrafluorofluoran(7.80 g, 15 mmol), zinc chloride (6.13 g, 45 mmol), zinc oxide (1.22 g,15 mmol), and 2-methyl-4-decyloxyaniline (7.89 g, 30 mmol) in sulfolane(30 g) was stirred with heating at 160-170° C. for 24 hours. Analysis byTLC (30% ethyl acetate/methylene chloride) showed a major product atRf=0.5 with a mass spectrum consistent with the product (M+1=751). Thereaction mixture was poured onto a mixture of ice/water/hydrochloricacid, stirred for ½ hour, filtered and dried. The crude product wasdissolved in ethyl acetate (700 mL) and stirred for one hour with 10%sodium bicarbonate solution (300 mL). After filtration through a pad ofCelite the organic layer was separated, dried over sodium sulfate andconcentrated to a thick oil. Column chromatography on silica gel (400 g,10-30% ethyl acetate/methylene chloride) provided pure fractions whichwere concentrated and recrystallized from acetone/hexane to yieldcolorless crystals (5.85 g), m.p. 137-139° C. A second crop (1.0 g) wasobtained to give a total of 6.85 g (9.12 mmol, 61% yield).

[0113] The structure was confirmed by NMR and mass spectroscopy.

Example IX Synthesis of Dye VIII

[0114] A mixture of3′-(5-methylindolino)-6′-chloro-4,5,6,7-tetrafluorofluoran (1.343 g, 2.5mmol), zinc chloride (1.022 g, 7.5 mmol), zinc oxide (0.203 g, 2.5mmol), and 2-methyl-4-decyloxyaniline (1.375 g, 5 mmol) in sulfolane (5g) was stirred with heating at 160-175° C. for 24 hours. The reactionmixture was poured onto a mixture of ice/water/hydrochloric acid,stirred for ½ hour, filtered and dried. The crude product was dissolvedin methylene chloride, treated with triethylamine (7 mL) and evaporated.Column chromatography on silica gel (250 mL, 50% ethyl acetate/methylenechloride) provided pure fractions which were concentrated andrecrystallized from acetone/hexane to yield colorless crystals (0.700 g,0.915 mmol, 37% yield) m.p. 170-171.5° C.

[0115] The structure was confirmed by NMR and mass spectroscopy.

Example X Synthesis of Dye IX

[0116] A mixture of 3′-indolino-6′-chloro-4,5,6,7-tetrafluorofluoran(1.0 g, 1.9 mmol), zinc chloride (0.8 g, 5.7 mmol), zinc oxide (0.2 g,2.8 mmol), and 2-methyl-4-octadecyloxyanilne (1.4 g, 3.8 mmol) insulfolane (4 g) was stirred with heating at 160° C. for 14 hours. Themixture was cooled to 50° C. and quenched into 2N HCl (100 mL). Thecrude solid was isolated by filtration, washed with water several timesand taken up in methylene chloride (150 mL). This methylene chloridesolution was washed with sat. sodium bicarbonate (2×100 mL) and driedover magnesium sulfate to remove the the solvent. The residual solid waspurified by column chromatography on silica gel eluted with 35% ethylacetate in methylene chloride to give pure product (1.0 g, 116 mmol, 61%yield) which was recrystallized from 10% acetone in hexane to givecolorless crystalline product (0.5 g, 0.57 mmol, 30% yield); m.p.136-138° C.).

[0117] The structure was confirmed by NMR and mass spectroscopy.

[0118] Although the invention has been described in detail with respectto various preferred embodiments, it is not intended to be limitedthereto, but rather those skilled in the art will recognize thatvariations and modifications are possible which are within the spirit ofthe invention and the scope of the appended claims.

What is claimed is:
 1. A compound represented by the formula

wherein: R₁, R₃, R₄, R₅, R₆ and R₇ are each independently selected fromthe group consisting of hydrogen, alkyl, substituted alkyl, alkenyl,substituted alkenyl, alkynyl, substituted, alkynyl, heterocycloalkyl,substituted heterocycloalkyl, substituted carbonyl, acylamino, halogen,nitro, nitrilo, sulfonyl, aryl, substituted aryl, heteroaryl,substituted heteroaryl, oxygen, substituted oxygen, nitrogen,substituted nitrogen, sulfur and substituted sulfur; R₂ is selected fromthe group consisting of hydrogen, alkyl, substituted alkyl, alkenyl,substituted alkenyl, alkynyl, substituted alkynyl, heterocycloalkyl,substituted heterocycloalkyl, substituted carbonyl, sulfonyl, aryl,substituted aryl, heteroaryl, substituted heteroaryl, substitutedoxygen, substituted nitrogen and substituted sulfur; R₈ is absent orselected from the group consisting of hydrogen, alkyl, substitutedalkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl,heterocycloalkyl, substituted heterocycloalkyl, substituted carbonyl,acylamino, halogen, nitro, nitrilo, sulfonyl, aryl, substituted aryl,heteroaryl, substituted heteroaryl, oxygen, substituted oxygen,nitrogen, substituted nitrogen, sulfur and substituted sulfur; R₉, R₁₀and R₁₁ are independently selected from the group consisting ofhydrogen, alkyl, substituted alkyl, alkenyl, substituted alkenyl,alkynyl, substituted alkynyl, heterocycloalkyl, substitutedheterocycloalkyl, substituted carbonyl, acylamino, halogen, nitro,nitrilo, sulfonyl, aryl, substituted aryl, heteroaryl, substitutedheteroaryl, oxygen, substituted oxygen, nitrogen, substituted nitrogen,sulfur and substituted sulfur; R₁₂, R₁₃, R₁₄ and R₁₅ are independentlyselected from the group consisting of hydrogen, alkyl, substitutedalkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl,heterocycloalkyl, substituted heterocycloalkyl, substituted carbonyl,acylamino, aryl, substituted aryl, heteroaryl, and substitutedheteroaryl; R₁₆, R₁₇, R₁₈ and R₁₉ are independently selected from thegroup consisting of hydrogen, alkyl, substituted alkyl, alkenyl,substituted alkenyl, alkynyl, substituted alkynyl, heterocycloalkyl,substituted heterocycloalkyl, substituted carbonyl, acylamino, halogen,nitro, nitrilo, sulfonyl, aryl, substituted aryl, heteroaryl,substituted heteroaryl, oxygen, substituted oxygen, nitrogen,substituted nitrogen, sulfur and substituted sulfur; and X₁ is carbon ornitrogen.
 2. A compound according to claim 1 wherein R₈, R₉, R₁₀ and R₁₁are halogen, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₁₂, R₁₃, R₁₄, R₁₅, R₁₆, R₁₇,R₁₈ and R₁₉ are as defined in claim 1 and X₁ is carbon.
 3. The imagingmember comprising a first image-forming layer including a compoundaccording to claim 1, said compound being in the crystalline form. 4.The imaging member as defined in claim 3 and further including asubstrate and at least a second color-forming layer, said secondcolor-forming layer being capable of forming a color different from thatformed by said first color-forming layer.
 5. The imaging member asdefined in claim 4 and further including a third color-forming layer,said third color-forming layer being capable of forming a colordifferent from those formed by said first and second color-forminglayers.
 6. The imaging member as defined in claim 5 wherein saidcolor-forming layers form magenta, cyan and yellow color, respectively.7. The imaging method comprising (a) providing an imaging member asdefined in claim 3; and (b) converting at least a portion of saidcompound to the liquid form in an imagewise pattern whereby an image isformed.
 8. The method as defined in claim 7 wherein step (b) comprisesapplying an imagewise pattern of thermal energy to said imaging memberwhereby at least a portion of said compound is converted to the liquidform and an image is formed.
 9. The thermal imaging method as defined inclaim 8 wherein said imaging member further includes a substrate and atleast a second color-forming layer, said second color-forming layerbeing capable of forming a color different from that formed by saidfirst color-forming layer.
 10. The imaging method as defined in claim 8wherein said imaging member further includes a third color-forminglayer, said third color-forming layer being capable of forming a colordifferent from those formed by said first and second color-forminglayers.
 11. The imaging method as defined in claim 10 wherein saidcolor-forming layers form magenta, cyan and yellow color, respectively.